The present invention relates to sound reproduction and more specifically to plural speakers compactly and divergently arranged to disperse sound generally equally in all directions.
Most examples of prior art reveal dual cabinets possibly containing multiple speakers located a distance apart at one end of the listening room on a baseline. This common arrangement is very directional and provides a line bisecting and normal to said baseline along which the listener must be positioned and at a proper distance from the arrangement in order to hear the sound from both cabinets in properly balanced relation.
Many attempts have been made to provide the listener with a larger listening area from which to hear properly balanced sound such as U.S. Pats. No. 2,710,662 to Camras and 3,933,219 to Butter both of which provide a unitary cabinet designed to direct the sound energy emanating from the speakers towards the rear wall of the listening room this sound energy being subsequently reflected off the side walls of the room toward the listener artifically separating the apparent source of sound beyond the walls of the room thereby creating an enlarged area of properly balanced sound energy. Another approach as set forth in U.S. Pat. No. 3,759,345 to Borisenko utilizes dual cabinets positioned in a conventional way but containing acoustic focusers which tend to direct the sound energy emanating from each speaker to the opposite side of the room such that a transverse shifting of the listener toward one side or the other maintains a more properly balanced distribution of sound from the two cabinets. These various solutions, although an improvement over their prior art, manipulate the sound escaping from their cabinets to direct said sound in a certain direction. Such manipulation involves certain distortions which the present invention seeks to reduce while retaining the advantage of an enlarged area of balanced listening from dual channel sound signal output.
In the art of sound reproduction besides the enhancement of stero separation many inventions are concerned with maximizing the qualit yof sound reproduced in a listening room. A speaker sealed into an infinite acoustic baffle is recognized as providing true and accurate sound reproduction through the elimination of interfering sound waves which inevitably emanate from the rear of a speaker. Such a baffle also eliminates the uncontrolled distortion of sound waves as they radiate outwardly from and collide with the edges and features of the conventional cabinet which is generally rectangular in shape. U.S. Pat. No. 4,268,719 to Manger demonstrates that the creation of this hitherto theoretical infinite acoustic baffle is possible simply by placing two similar speakers back to back and exciting said speakers in unison. The baffle is created along a common plane between the speakers thereby cancelling out interference from the rear of the speakers and enhancing the distributed sound measurably. According to the Manger patent, the effect is present even when said speakers are divergently aligned, as long as their central axes intersect at a common point.
The present invention places more than three speakers in divergent alignment about a common point such that said speakers share a common angle of divergence with all adjacent speakers. For instance, U.S. Pat. No. 4,268,719 is primarily concerned with two speakers mounted at an angle of divergence of 180 degrees. The improvement herein described places for example four similar speakers at a common angle of divergence of 109.47122 degrees between the axes of adjacent speakers thereby reproducing said infinite acoustic baffle as a series of flat planes radiating outwardly from the centre of the arrangement between adjacent speakers and thereby separating the output of said speakers one from another. As long as the angle of divergence between adjacent speakers is equal and said speakers are exicted in phase, this infinite acoustic baffle is created in the form of a regular geometric pyramid coaxial with each speaker and having an open and outwardly facing base said base being at an infinite distance from the centre of this arrangement.
Several examples of prior art such as U.S. Pat. No. 4,299,304 to Rebsch describe the advantage of an exponential horn when mounted coaxially with the output side of a speaker. In fact the Rebsch patent by placing the speaker coaxially with the cooperating plane surfaces in the corner of a room utilizes these surfaces to create an infinite horn that occupies one eighth of the volume of a sphere. The present invention can reproduce a similar condition by utilizing the principle of the infinite acoustic baffle to create said horm by placing eight speakers in balanced divergence about a common point. With eight speakers the common angle of divergence is 70.52878 degrees between the axes of adjacent speakers. Therefore the present invention can utilize the advantages of the exponential horn without having to resort to remote speaker placement such as that of U.S. Pat. No. 4,299,304 or additional construction of any king.